Use of intrathecal SNX-111, a novel, N-type, voltage-sensitive, calcium channel blocker, in the management of intractable brachial plexus avulsion pain

Objective: The objective was to assess the analgesic, antihyperesthesic, and antiallodynic properties of SNX-111 in neuropathic pain. Design: We describe a patient with refractory, severe deafferentation pain successfully treated with SNX-111 in an open-label, baseline-controlled Phase I/II trial. Setting: The patient was hospitalized for treatment and observation. Patient: The patient was a 43-year-old man with intractable deafferentation pain of 23 years' duration secondary to brachial plexus avulsion. Intervention: SNX-111, the first neuron-specific, N-type, voltage-sensitive calcium channel blocker developed for clinical use, was administered by continuous, constant-rate, intrathecal infusion via an indwelling cervical catheter. Outcome Measures: The primary outcome measures were the Visual Analog Scales of Pain Intensity (VASPI) and Pain Relief (VASPR). Results: The patient experienced complete pain relief (VASPI = 0.0 cm and VASPR = 10.0 cm) with elimination of hyperesthesia and allodynia. Conclusions: SNX-111, administered intrathecally by continuous, constant-rate infusion, produced dose-dependent pain relief in a 43-year-old male patient with a 23-year history of intractable deafferentation and phantom limb pain secondary to brachial plexus avulsion and subsequent amputation. Dizziness, blurred vision, and lateral-gaze nystagmus were dose-dependent side effects that resolved with decreasing dose levels. Complete pain relief was achieved in this patient without side effects after dose adjustment. We conclude that SNX-111 is a potent analgesic, antihyperesthesic, and antiallodynic agent. Controlled studies of SNX-111 in patients with malignant and nonmalignant pain syndromes are warranted and are under way.